fix: fix button clear issue.

demo/Ursa.Demo/Pages/TimePickerDemo.axaml

@@ -19,6 +19,7 @@
             PanelFormat="hh mm tt" />
         <u:TimePicker
             Width="300"
+            Classes="ClearButton"
             DisplayFormat="HH 时 mm 分 ss 秒"
             PanelFormat="HH mm ss tt"
             HorizontalAlignment="Left"

src/Ursa.Themes.Semi/Controls/TimePicker.axaml

@@ -123,11 +123,10 @@
                             BorderBrush="{TemplateBinding BorderBrush}"
                             BorderThickness="{TemplateBinding BorderThickness}"
                             CornerRadius="{TemplateBinding CornerRadius}" />
-                        <Grid ColumnDefinitions="*, Auto, Auto">
+                        <Grid ColumnDefinitions="*, Auto">
                             <TextBox
                                 Name="{x:Static u:TimePicker.PART_TextBox}"
                                 Grid.Column="0"
-                                Grid.ColumnSpan="2"
                                 HorizontalAlignment="Stretch"
                                 VerticalAlignment="Stretch"
                                 Background="Transparent"
@@ -172,7 +171,7 @@
                                 Theme="{DynamicResource InnerIconButton}" />
                             <Button
                                 Name="{x:Static u:TimePicker.PART_Button}"
-                                Grid.Column="2"
+                                Grid.Column="1"
                                 Padding="0,0,8,0"
                                 Content="{DynamicResource TimePickerIconGlyph}"
                                 Focusable="False"
@@ -234,6 +233,9 @@
             <Style Selector="^:pointerover /template/ Button#ClearButton">
                 <Setter Property="IsVisible" Value="{Binding $parent[u:TimePicker].SelectedTime, Converter={x:Static ObjectConverters.IsNotNull}}" />
             </Style>
+            <Style Selector="^:pointerover /template/ Button#PART_Button">
+                <Setter Property="IsVisible" Value="{Binding $parent[u:TimePicker].SelectedTime, Converter={x:Static ObjectConverters.IsNull}}"/>
+            </Style>
         </Style>
 
         <Style Selector="^:pointerover">

src/Ursa/Controls/DateTimePicker/TimePicker.cs

@@ -118,7 +118,7 @@ public class TimePicker : TemplatedControl, IClearControl, IInnerContentControl,
 
     public void Clear()
     {
-        SetCurrentValue(SelectedTimeProperty, null);
+        _presenter?.SetValue(TimePickerPresenter.TimeProperty, null);
     }
 
     public object? InnerLeftContent